Periodic unacceptable high forces generated by the wheel-rail interaction of a moving railway wagon may be harmful to the wheels, the bogies, the wagon and the rail. If the wagon operates with defective bogies, including flat wheels, over a period of time, the resultant damage may be costly in terms of wheel or rail wear or in extreme cases result in dangerous derailments. The degree of this danger may be much more severe if the railway wagon carries hazardous material.
Technology has been developed to monitor performance characteristics of a railway wagon and the rail track in order to detect conditions that may cause damage or derailment. For example, the truck/bogie performance has been measured by utilizing wayside sensing, which measure forces at the wheel-rail interface. The wayside technology may measure and detect bogies or wheel sets that are not performing correctly, and communicate this information back to a central office, so that the bogies or wheel sets could be removed for service and inspection. This technology has inherent disadvantages, however, in terms of costs and the multiple locations across large rail systems required to identify the wagons that are not performing safely.
A wheel flat (also known as flat spot) is a well-known defect related to the tread shape of a railroad wheel, which decreases the roundness of a wheel. A wheel flat may for example develop if the wheel set of a railroad wagon is being dragged along the rail after the wheel-axle set has stopped rotating. Faulty brakes or faulty wheel set bearings, or other conditions that causes the wheel to lock up while the railroad wagon is still moving, may thus cause a wheel flat. Often, a wheel set must be replaced or the wheel set turned if a large flat spot is detected, since a wheel flat may cause serious derailment.
To summarize, for safety reasons, there is a need in the art for a method of detecting a wheel-flat at an early stage so that required actions may be performed to preclude derailment.